I agree. Just drop two jet sizes and see how it reacts. Then you can go down one or two more if it needs it. 68 is not an uncommon primary jet to run.
I would also offer a word of caution on the head porting. Dont do anything extravegant. Search for "pocket porting" or "bowl porting" on this site and you will find lots of information. That and the gasket matching are all you want to do without a flow bench. Just hogging out the ports could end you up with a real dog or useless heads.